1. Field of the Invention
The present invention relates to a rotary nozzle which is attached to the bottom shell of a molten steel vessel such as a ladle or tundish whereby a slide plate brick is rotated so as to adjust the degree of opening of nozzle bores depending on the relation between the slide plate brick and the fixed plate brick to control the rate of pouring of molten steel.
2. Description of the Prior Art
Rotary nozzles have been used widely with ladles for receiving the molten steel tapped from a converter to transport or pour the molten steel into molds, tundishes for receiving the molten steel from a ladle to pour the molten steel into molds and the like. In particular, the rotary nozzles of the hinged type in which a rotor including a slide plate brick is opened and closed by rotating it by a hinge have recently been used in great number due to its various advantages that the sliding surfaces can be exposed so as to confirm for example the damages to the plate surfaces of the fixed plate brick and the slide plate brick with the naked eye, that there is no need to prepare any stand-by set in case of the changing or the maintenance and repair of the bricks, that the operation is easy and so on.
Such rotary nozzle of the hinged type is pivotably fitted to the base member attached directly or through a member to the bottom shell of a ladle, tundish or the like (hereinafter referred to as a molten steel vessel) and the reduction gear output from a driving source, e.g., a motor is transmitted through an intermediate gear to the gear of the rotor including the slide plate brick, mounted in a door, thus rotating the rotor and hence the slide plate brick and thereby adjusting the opening of the nozzle.
FIG. 6 is a sectional view of an example of the conventional rotary nozzle. In the Figure, numeral 51 designates the bottom shell of a molten steel vessel, and 52 a base member attached to the bottom shell 51 with bolts 53 and a fixed plate brick 54 is mounted in the base member 52. Numeral 56 designates a top nozzle projected through a bore formed through the bottom shell 51 of the molten steel vessel and the base member 52 and connected to a nozzle bore 55 of the fixed plate brick 54. Numeral 57 designates a fixed frame pivotably attached to the base member 52 by a hinge 58. Numeral 59 designates a rotor received in the fixed frame 57, arranged rotatably on a bearing guide 62 through a ball bearing 60, formed on the outer periphery thereof with a gear 61 meshed with a gear (not shown) connected to the driving source and receiving a slide plate brick 63 in the upper part thereof. Numeral 65 designates a collector nozzle connected to a nozzle bore 64 of the slide plate brick 63, and 66 a nozzle bore in the collector nozzle. Numeral 67 designates a plurality of spring seats which are provided within the fixed frame 57 to face the bearing guide 62 with a coil spring 68 being mounted between each of the spring seats and the bearing guide 62. Thus, a door 70 is formed by the fixed frame 57, the rotor 59, etc.
With the rotary nozzle constructed as described above, during the pouring of molten steel the door 70 is closed and fastened to the base member 52 so that the slide plate brick 63 is pressed against the fixed plate brick 54 by the coil springs 68 and there is no danger of the leakage of the molten steel. It is to be noted that if necessary, the rotor 59 is rotated from the driving source and the degree of opening of the nozzle bores 55 and 64 is adjusted, thereby controlling the pouring rate of the molten steel. Also, in order to effect the maintenance and inspection of the change of the fixed plate brick 54 and the slide plate brick 63, the door 70 can be pivoted on the hinge 58 to open the door 70.
The rotary nozzle of the above type has been widely put in practical use as a device for controlling the pouring rate of molten steel by virtue of the fact that it is small in size, light in weight and positive in operation. However, this type of rotary nozzle is disadvantageous in that while the center lines of the nozzle bores 55 and 64 of the fixed plate brick 54 and the slide plate brick 63 are in alignment as shown in FIG. 6 when these nozzle bores are fully open, when the slide plate brick 63 is rotated to reduce the degree of opening of the nozzle bores 55 and 64, there is caused a deviation between the center line of the nozzle bore 55 of the fixed plate brick 54 and the center line of the nozzle bores 64 and 66 of the slide plate brick 63 and the collector nozzle 65 as shown in FIG. 7 with the result that the molten steel emerging from the nozzle bore 55 of the fixed plate brick 54 changes its direction to fall towards the inner wall of the nozzle bore 66 of the collector nozzle 65 and thereby damaging the inner wall of the nozzle bore 66 of the collector nozzle 65 and also the solidified steel is accumulated on the inner wall thereby extremely reducing the life of the expensive collector nozzle 65.
Further, with the latest rotary nozzles of the type used for the continuous casting of steel, while it is essential to provide a long nozzle 71 below the collector nozzle 65 as shown in FIG. 7, the long nozzle 71 is fixed in place in a manner that its nozzle bore 72 is positioned in alignment with the nozzle bore 55 of the fixed plate brick 54 with the result that when the nozzle bores 55 and 64 are reduced in the degree of opening, there is the danger of the nozzle bore 66 of the collector nozzle 65 shifting from the nozzle bore 72 of the long nozzle 71 and thereby failing to pour the molten steel. As a result, the supporting member of the long nozzle 71 is provided with a joint to make a so-called oscillatory motion and this has not only the undesirable effect of making the construction extremely complicated and expensive but also the effect of making difficult the sealing between the molten steel vessel and the long nozzle 71 due to the movement of the long nozzle 71. In addition, where the long nozzle 71 is inserted into a center runner such as a bottom pouring runner to pour the molten steel, there are many difficulties that the movement of the long nozzle 71 causes it to strike against the center runner and so on.
The invention disclosed in Japanese Laid-Open Patent No. 47-05905 is an example of the proposals heretofore made to overcome the foregoing problems of the conventional rotary nozzle. This invention is constructed so that the axis of rotation of an elongated frusto-conical slide member is arranged to make an acute angle (7 degrees according to an embodiment) with the central axis of a flow passage through the slide member and the outlet opening of the slide member flow passage is maintained at the same position in response to all the positions of the slide member, with the result that the outflowing molten material passes freely and vertically through the flow passage at the position of the slide member which completely opens the flow passage and the position of the nozzle bore in the lower part of the collector nozzle is not allowed to deviate at the throttled slide member positions.
Also, the invention disclosed in Japanese Laid-Open Patent No. 2-263562 consists in a rotary nozzle which is intended to attain the same purpose as mentioned above and in which a discharge block contacting an annular supporting casing has an outer peripheral surface whose contacting portion is formed of a spherical shape, thereby making uniform the pressure at the close contacting sliding surfaces of an upper block and the discharge block.
In accordance with the invention disclosed in Japanese Laid-Open Patent No. 47-5905, a perforated plate is supported below a casing so that the static pressure of molten steel is directly applied to the perforated plate and an excessive interfacial pressure is produced at the contact surface between the perforated plate and the lower part of the casing, thereby giving rise to the danger of damaging the perforated plate.
Further, in accordance with Japanese Laid-Open Patent No. 47-5905 and Japanese Laid-Open Patent No. 2-263562, respectively, a slide plate brick and a colletor nozzle are combined as a unit to form a slide member or a discharge block thus making the manufacture difficult. Particularly, in the case of the latter invention, the rotary nozzle is constructed so that the discharge block contacting with the annular supporting casing has an outer peripheral surface formed of a spherical shape to follow up an inclination error and therefore not only is the construction complicated and the working is difficult but also the follow-up fails to take place if the sliding of the spherical surface is not good thereby deteriorating the reliability. Also, since the slide member or the discharge block is pressed against the performed plate or the upper block by simply fastening the casing in place with bolts directly or through spring packs, the two are not uniform in contract pressure and the molten steel tends to leak; particularly, the two cannot be contacted closely if the precision of the inclined surface is not satisfactory.
Further, since the lower end portion of the slide member or the discharge block is in the form of an inclined surface, the connection with the fixedly arranged long nozzle is extremely troublesome.
Still further, the former is so designed that the supporting ring supporting the slide member is provided with external teeth and the rack engaging with the external teeth is driven by the operating cylinder thereby rotating the slide member, the driving mechanism and hence the whole apparatus is extremely increased in size. On the other hand, the rotary nozzle of the latter invention has many disadvantages that the supporting , 987ng supporting the discharge block is provided with a worm gear so as to rotate it by a worm so that during the rotation of the worm gear the sliding surfaces of the discharge block and the upper block are separated thus giving rise to the danger of frequently causing troubles of molten steel leakage and so on and therefor its realization is difficult.